Numerous and varied methods have been derived for determining the torque on a rotating system. Some examples of known methods include the use of magnetic brakes, strain gage transducers, and system drive motor current. To implement the first method, a magnetic brake with a known magnetic field based on a current and associated reaction torque is coupled to a rotary portion of the system. During operation, the current supplied to generate the magnetic field is used to determine the applied torque. To implement the second method, a strain gage transducer is coupled to the rotating portion of the system and signals and power transferred across slip rings. Torque is derived based on the torsional stress in the shaft to which the gage is coupled. To implement the third method, a drive motor with a known torque constant is coupled to and drives the rotating portion of the system. The torque is then determined using the known torque constant and the current supplied to the system.
Each of the above methods has its advantages. However, because each relies on a component being mechanically coupled, in one fashion or another, to the rotating system, these methods are unsuitable for determining the torque in an environmentally isolated rotating system with sufficient accuracy.
Hence, there is a need for a system and method for determining torque in an environmentally isolated rotating system that does not rely on mechanical coupling to, or contact with, the rotating system. The present invention addresses at least this need.